1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, the present invention relates to a method of manufacturing a thin film resistor layer.
2. Description of the Related Art
The resistor is one of the most common electrical components and is widely used in almost every electrical device. A semiconductor device, mostly an integrated circuit, including memories and logical devices, normally consists of resistors and other electrical components. The resistance provided by a resistor is proportional to the length of the resistor and the reciprocal of the cross-sectional area of the resistor; both are measured in the direction of the current. That is, the resistance of a resistor fulfills the following equation: ##EQU1## wherein .rho. is the resistivity of the resistor, L and A are the length and the cross-sectional area of the resistor, respectively, and wherein both L and A are measured in the direction of the current.
Conventionally, doped polysilicon is used as the material of a resistor in a semiconductor fabrication process, wherein the resistance is controlled by predetermined L and A of the doped polysilicon layer.
As the integration of a semiconductor device is increased, all components within a semiconductor integrated circuit have to provide equivalent or better electrical properties. Hence, a downsized resistor still has to provide a required resistance. However, a conventional resistor made of doped polysilicon can only provide a limited resistance within a limited space because of the property of polysilicon. Using a polysilicon resistor to provide a relatively high resistance then becomes a problem in designing and fabricating a highly integrated semiconductor device.
For overcoming the foregoing problem, new materials like CrSi having a higher resistivity than that of polysilicon are applied in the fabrication of a thin-film resistor of a highly integrated semiconductor device.
However, when the CrSi is immediately exposed in the plasma process, the chemistry of the CrSi is destroyed. Therefor, in the process for patterning a CrSi layer, an aluminum layer or an aluminum alloy layer is used as a protective layer to protect the CrSi layer from the damages caused by the plasma. Since titanium reacts with aluminum in a subsequent inter-metal connects process, it is impossible to use a titanium layer as a barrier layer. Incidentally, the sidewall of the patterned CrSi layer is not protected by the protective layer. In a subsequent inter-metal connects process, the sidewall of the CrSi layer uncovered by the protective layer is electrically coupled to the wire formed above the CrSi layer, which is caused by process inaccuracy, so that the directions of current flow are increased and the resistance of the CrSi layer changes. Hence, the electrical operation of the devices changes.